Gasport limestone member of Lockport dolomite described as light-gray to white coarse-grained semicrystalline crinoidal limestone, generally non-magnesian. Thickness 6 to 20 ft. In literature has been called Lower Niagara limestone, Lockport Encrinal marble, and Crinoidal limestone. Overlain by dark-gray to chocolate-colored saccharoidal dolomite; underlain by drab magnesian limestone [later named De Cew limestone]. Silurian age assigned.

Source: GNU records (USGS DDS-6; Reston GNULEX).

Lockport Group in this report is considered Late Silurian following Rickard (1975) as the NY Geological Survey does not recognize Middle Silurian as does the USGS. The revisions to the Lockport nomenclature discussed in this report will be formally proposed by C.E. Brett in a larger study of the Niagaran Series. The Lockport Group is divided into the (ascending) Gasport Limestone, the Goat Island Dolomite, the Eramosa Dolomite, and the Guelph Dolomite. The Gasport includes the Gothic Hill and Pekin Members, and the Goat Island includes the Niagara Falls, Ancaster, and Vinemount Members. [Though three of the authors of this report (Tepper, Kappel, and Yager) are USGS scientists, the nomenclature used here has not been officially accepted for use by the USGS.]

Source: GNU records (USGS DDS-6; Reston GNULEX).

Nomenclature in this report follows Brett and others (in press). Gasport Formation is divided into lower Gothic Hill Member and Pekin Member. Occurrence of graptoloid graptolites in the overlying Niagara Falls Member of the Goat Island Formation indicates Wenlockian-Ludlovian boundary is located at top of Gasport. Previously this boundary had been placed much higher in the section.

Source: GNU records (USGS DDS-6; Reston GNULEX).

Revised the Gasport to the Gasport Dolomite of the Lockport Group and divided unit into two members, the Gothic Hill and Pekin Members. Gasport consists of a lower light pinkish-gray, crinoidal- and brachiopod-rich dolograinstone to dolopackstone (Gothic Hill Member) and an upper dark olive-gray, argillaceous, fine- to medium-grained dolomicrite that grades laterally into bioherms and flanking dolorudites (Pekin Member). Thickness is 19.5 to 37.2 ft. Unconformably overlies the DeCew Dolomite of the Clinton Group and unconformably underlies the Goat Island Dolomite of the Lockport Group. The Gasport is of Early Silurian (Wenlockian) age based on conodonts. [Report uses Early and Late Silurian time scale of Harland and others (1982).]

Source: GNU records (USGS DDS-6; Reston GNULEX).